U.S. Pat. No. 6,097,536 describes an assembly including a holder and a component (optical component) adhesively bonded via an adhesive. The component transmits radiation in the ultraviolet spectral range. The adhesive is curable by UV light. Between the transparent component and the adhesive, a thin radiation protective layer is applied in the region of the adhesive. To protect the adhesive against UV radiation, the thin layer transmits light in a spectral range suitable for the curing of the adhesive, e.g. at the mercury I-line 365 nm, and the thin layer highly reflects or absorbs UV light from a used spectral range within the spectral range transmitted by the transparent component. The radiation protective layer includes a material selected from tantalum pentoxide, hafnium dioxide, titanium dioxide, zinc sulfide, cerium fluoride, magnesium fluoride, cryolite or mixtures thereof.
In addition or as an alternative to the protection of an adhesive, however, a radiation protective layer can also be of advantage for protecting a fluid-repellent layer, e.g. a water-repellent layer, against UV radiation, as is described for example in WO 2008/031576 A1 of the present applicant. Such a water-repellent layer or coating can include, e.g., silanes, siloxanes, diamond-like carbon (DLC), fluorides, hydrophobic varnishes and adhesives, and also of polymers, in particular of fluoropolymers, such as are sold for example under the name Optron, WR1 and Teflon AF. In this case, the material of the fluid-repellent layer can likewise be curable by (UV) radiation or thermally curable (e.g., Ormocer). Fluid-repellent layer materials, too, are typically not stable over the long term if they are exposed to UV light at radiation intensities such as are customary in microlithography. However, other components, too, e.g., seals, are possibly not stable over the long term and can be protected against UV radiation having high intensity with the aid of a radiation protective layer.
The radiation protective layer is desirably opaque to radiation in the (UV) spectral range transmitted by the optical component. In addition, the radiation protective layer desirably has a sufficient transmission in the spectral range used for curing the adhesive or, if appropriate, the fluid-repellent material. Further, the radiation protective layer should have a good adhesion on the optical component and also a sufficient adhesion for the applied adhesive or the fluid-repellent layer. Moreover, the radiation protective layer should have no adverse influence on the curing of the adhesive or the fluid-repellent material. The radiation protective layer should also be water-insoluble and have a high aging stability particularly with respect to short-wave (UV) radiation.